Expression of Na+,K+-ATPase β subunit isoforms in the European eel (Anguilla anguilla)

Reverse transcriptase - polymerase chain reaction experiments utilising degenerate primers were used to demonstrate that the Na+,K+-ATPase beta 3 but not beta 2 isoform was present in brain tissue from the European eel (Anguilla anguilla). Two cDNA fragments were cloned and sequenced yielding 445 nucleotides of the Na+,K+-ATPase beta 3 isoform sequence. The putative amino acid sequence translated from this nucleotide sequence shared 58.0, 50.6 and 50.3% homology with previously published Na+,K+-ATPase "beta 3-like" isoform sequences from the clawed toad (Xenopus laevis), the chicken (Gallus domesticus) and the toad (Bufo marinus) respectively. The size of the Na+,K+-ATPase beta 3 mRNA transcript in eel tissues was demonstrated to be 2.4 Kb. Detectable levels of Na+,K+-ATPase beta 3 mRNA were only found in brain tissue. The tissue specific distribution of the beta 3 mRNA suggests that it plays little or no direct role in the process of osmoregulation in tissues such as the intestine or gill.